Coating processes are used in many areas of the art. In particular, the manufacture of diagnostic test elements useful in measuring biological analytes such as blood glucose require generating different layer films on a solid support. Theses layers are obtained by a coating process where one or more coating compositions are applied to the solid support. Typical diagnostic test elements and coating processes for generating the same are described in, for example, DE Patent Application Publication Nos. 196 29 656 and 196 29 657, Int'l Patent Application Publication No. WO 2010/052306, and EP Patent No. 0 821 234.
However, it is decisive for reliably working diagnostic test elements that the quality of the coat can be assured. To this end, it is necessary to characterize the coat (i.e. the layers) by determining the amount of dried coating composition that forms the coat. Such characterizing is required to assess the quality of the coat in the context of desired specifications.
Currently, the amount of dried coating composition applied to a solid support is determined by differential weighing (i.e., by weighing the amount of coating composition prior and after application). Thereby, the amount of coating composition that has been applied can be calculated. Moreover, the amount of dried coating composition is subsequently determined by calculating the sum of the amounts of the solid components of the composition.
Differential weighing also may be used to determine the applied dried coating composition directly. To this end, the solid support with the coat of dried coating composition is weighed first. Afterwards, the dried coat is completely removed from the solid support (e.g., by ultrasound treatment), and the solid support without the coat is weighed again. The determined difference of the weights represents the amount of dried coating composition applied as a coat to the solid support.
Likewise, the amount of dried coating composition in a coat can be determined by infrared (IR) spectroscopic techniques or can be determined with heavy elements by X-ray fluorescence (for determining heavy elements by X-ray fluorescence, see, Rizescu (2001) Int'l J. Energ. Environ. 4:503-513; and Ene (2010) Rom. J. Phys. 55:815-820). These techniques, however, are sensitive to matrix effects of the coat or require the addition of high concentrations of heavy elements to the coat.
Thus, there is a need for improved methods of determining the quality of coats and, in particular, of applied dried coating compositions.